1. Field of the Invention
The present invention relates to an ink jet recording apparatus for performing a recording operation by discharging ink from a recording head mounted to a carriage which is reciprocally shifted toward a recording medium, and a cleaning mechanism portion of such a recording apparatus.
2. Related Background Art
In serial type recording apparatuses having a serial scan system for performing a main scan along a direction transverse to a conveying direction (sub scan direction) of a recording medium, the entire recording medium is recorded by repeating operations in which an image is recorded by a recording head (recording means) mounted on a carriage that is shifted along the recording medium (main scan) and, after one line of recording is finished, the recording medium is fed by a predetermined amount (pitch conveyance) and a next line image is recorded (main scan).
Among the above-mentioned recording apparatuses, an ink jet recording apparatus is of a type in which a recording operation is performed by discharging ink from the recording means (recording head) onto the recording medium and can achieve compactness of the recording means, can record a highly fine image at a high speed and can record the image on plain paper without specific treatment. Further, the ink jet recording apparatus has advantages such as the running cost is inexpensive and the noise generated is less because the ink jet recording apparatus records using a non-impact system, and a color image can easily be recorded by using multi-color inks.
The recording head used in the ink jet recording apparatus includes an ink flow path extending from an ink reservoir (ink tank portion) to an ink discharging portion and, whenever the ink is discharged, new ink is successively supplied from the ink reservoir to the ink discharging portion. In the recording apparatus utilizing such a recording head, it is practical to provide a cleaning mechanism portion (recovery mechanism portion) for cleaning the recording head for the purpose of obtaining good image quality by stabilizing an ink discharging operation when the ink tank is replaced by a new ink tank after the ink in the ink tank is used up and the ink is re-filled in the flow path extending to the ink discharging portion or when foreign matter such as solidified ink, dirt and/or bubbles in the vicinity of an ink discharge port are removed (cleaned).
FIG. 20 is a schematic front view showing a cap open condition of the cleaning mechanism portion of a conventional ink jet recording apparatus. FIG. 21 a fragmental schematic front view showing a cap closed (capping) condition of the cleaning mechanism portion of FIG. 20. In FIGS. 20 and 21, a carriage 6, on which a recording head is mounted, is shifted in a main scan direction relative to a recording medium, such as a paper, to provide shifting and guiding movements by means of guide shafts 101a and 101b provided on a chassis 101. A part of a timing belt 103 is connected to the carriage 6, and the carriage 6 is driven along the guide shafts 101a and 101b by transmitting a rotation of a CR (carriage) motor 102 that is secured to the chassis 101 to the timing belt 103.
A cleaning mechanism portion 108 is provided, at a base side of a main body of the recording apparatus, at a position facing the recording head mounted on the carriage 6. The cleaning mechanism portion 108 is provided with a cap 104 for covering a discharge port face of the recording head. The cap 104 is used to prevent solidification of the ink and increase in viscosity of the ink in the vicinity of discharge ports by covering the discharge port face of the recording head in a record waiting condition, and to suck the ink from the discharge ports by generating negative pressure in the cap when processing for recovering clogging of the discharge ports, by connecting the cap to a negative pressure generating source. The cap 104 is formed from elastic rubber material or the like. The cap 104 is held by a cap holder 105, and the cap holder 105 holding the cap 104 is slidably mounted on a cap slider 106. A cap spring 107 is mounted between the cap holder 105 and the cap slider 106.
A shaft portion 106a provided on the cap slider 106 is supported so as to enable shifting and guiding movements along a cam surface (shown by chain double-dashed line) provided in the base portion of the main body of the recording apparatus. Further, the cap slider 106 is provided with an abutment portion 106b, which can abut against a side surface of the carriage 6, and, accordingly, after the carriage 6 enters into the cleaning mechanism portion 108 to abut against the abutment portion 106b, the cap slider 106 can be shifted in synchronism with the shifting movement of the carriage in accordance with the main scan shifting of the carriage 6. Further, the cap slider 106 is connected to the main body of the recording apparatus by means of a tension spring 109 so that, when the carriage 6 is not in the cleaning mechanism portion 108, the cap slider is held at a predetermined waiting position shown in FIG. 20 by means of the tension spring 109. Namely, in the cleaning mechanism portion 108 having the above-mentioned construction, when the carriage 6 enters into the cleaning mechanism portion 108, the side surface of the carriage 6 abuts against the abutment portion 106b of the cap slider to start the synchronous shifting movement, with the result that the cap slider 106 can similarly be shifted (slid) by the shifting (operation) of the carriage 6.
When the carriage 6 further advances in the cleaning mechanism portion 108, the cap slider 106 is gradually lifted toward the recording head by the action of the cam surface (shown by the chain double-dashed line) of the main body of the recording apparatus. As a result, the cap 104 abuts against the discharge port face of the recording head to establish the capping condition. In this capping condition, under the action of the spring pressure of the cap spring 107, the cap 104 is closely contacted with the discharge port face of the recording head. By waiting in a condition that the cap 104 is closely contacted with the recording head (condition that the discharge ports are sealed) in this way, the discharge ports and the discharge port face of the recording head can be protected.
Further, a suction tube 110 is connected to the cap 104 via the cap holder 105 and the other end of the suction tube 110 is connected to the negative pressure generating source (pump portion). Accordingly, in the condition that the cap 104 is closely contacted with the recording head, by operating the negative pressure generating source, the negative pressure can be created within the cap 104 through the suction tube 110 and the ink can be sucked from the discharge ports of the recording head by the negative pressure. Such ink suction is suction recovery processing for eliminating the clogging of the discharge ports and is one of the primary functions of the cleaning mechanism portion 108.
In the recording operation, when the shifting direction of the carriage 6 is reversed so that the carriage 6 is shifted again away from the cleaning mechanism portion 108, the cap slider 106 is gradually moved from the discharge port face of the recording head to establish the cap open condition, with the result that the image can be recorded on the recording medium by the operations of the carriage 6 and the recording head. In this way, the cleaning operation for the recording head can be performed in accordance with the position of the carriage 6 and the action of the cleaning mechanism portion (pump mechanism portion or the like).
However, the above-mentioned conventional arrangement has the following problems:
1) In the condition that the recording head is located at the capping position, after the pump mechanism is activated to suck the ink, when the carriage is shifted away from the cleaning mechanism portion to separate the recording head from the cap, a large amount of ink remains on the discharge port face of the recording head. Since ink remains on the adjacent different color ink discharge ports (discharge port arrays), different color inks may be mixed during the recording operation.
2) Further, when a large amount of ink remains on the discharge port face of the recording head, even if the ink remaining on the discharge port face is wiped by a blade (wiping processing) after the cleaning operation, the ink cannot be removed fully, and the residual ink may be readily applied to the surface of the paper.
3) When the recording head is left in the capping condition for a long time, the ink remaining in the cap may solidify and become adhered between the recording head and the cap. As a result, when the carriage moves away from the cleaning mechanism portion to start the recording operation, since the cap is stuck to the recording head, the recording head cannot be separated from the cap, which may lead to poor operation of the carriage. In the worst case, the cleaning mechanism portion may be damaged.
4) When the carriage enters into the cleaning mechanism portion to cap the recording head, the cap slider holding the cap is slid upwardly along the cam surface of the main body of the recording apparatus to abut the cap against the recording head. Thus, the reaction force of the cap spring (cap abutting force) also acts as the sliding load of the carriage, with the result that a carriage motor providing adequate torque must be used. Consequently, from the viewpoint of compatibility between the required driving torque and the recording quality and the cost, the selection of the motor to be used will be limited. Further, if the cam surface of the main body of the recording apparatus is made to have a gentle cam slope to reduce the sliding resistance of the carriage, when the cleaning processing of the recording head is performed by the cleaning mechanism portion, a shifting range of the carriage is widened, with the result that it becomes difficult to reduce the size of the main body of the recording apparatus.